The present invention relates to a sliding member provided with a sliding layer on a surface of a base material formed of any of steel, stainless steel, copper-based alloy, aluminum-based alloy, and magnesium-based alloy.
As an example, a sliding member provided with sliding layers on the surfaces of a base material formed of steel has been used, for example, for a swash plate etc. of a swash plate type piston pump (variable displacement pump, compressor, etc.). The swash plate type piston pump is constructed so that a gas in a cylinder is compressed by a piston reciprocating in the cylinder following a rotating swash plate. In the pump of this type, the swash plate slides with respect to a shoe, which is a mating member interposed between the swash plate and the piston. The swash plate of the swash plate type piston pump rotates at a high speed and also receives a high pressure from the shoe.
Conventionally, as the above-described sliding member used for a swash plate type compressor and the like equipment, a sliding member in which coating layers consisting of a solid lubricant using polyamidimide (hereinafter abbreviated to “PAI”), polyimide (hereinafter abbreviated to “PI”), or epoxy (hereinafter abbreviated to “EP”) as a binder are formed on both surfaces of a base material has been proposed in JP-A-4-83914, JP-A-9-79262, JP-A-8-59991, etc.
On the other hand, in the above-described sliding member, a lubricating oil is supplied onto the sliding surface, and in particular, in the above-described swash plate type compressor or the like, a mixture of a refrigerant and a refrigerating machine oil, which is a lubricating oil, (refrigerant/refrigerating machine oil mixture) is supplied. Thus, the lubricating oil is supplied onto the sliding surface of sliding member. In a case where the equipment is not used for a long period of time, for example, as in the case of the compressor for an air conditioner, the refrigerant/refrigerating machine oil mixture becomes absent on the sliding surface of sliding member, and hence the sliding surface becomes in a dry state. If the compressor is started in this state, since some period of time is required before the refrigerant/refrigerating machine oil mixture is supplied onto the sliding surface, the sliding member slides in the dry state until the refrigerant/refrigerating machine oil mixture is supplied, so that a high load is applied to the sliding member, and thus the sliding member may seize. Therefore, there has been demanded a sliding member which can slide for a long period of time without seizing even in the dry state before the refrigerant/refrigerating machine oil mixture is supplied sufficiently.
The above-described sliding member in which coating layers formed of a solid lubricant using PAI, PI, EP, etc., which are thermosetting resins, as a binder, are formed on both surfaces of a base material presents a problem in that the base material is exposed in a short period of time by the wear of the sliding layer caused by the use in a dry state, and resultantly seizure occurs. The present invention has been made in view of the above situation, and accordingly an object thereof is to provide a sliding member which can slide for a longer period of time even in a dry state.